Field of the Invention
The present invention relates to a band pass filter formed to include a conductive pattern and a capacitor on a substrate on which a plurality of layers are laminated, capable of easily setting a desired attenuation frequency by adjusting an amount or a shape of via holes provided in the substrate, and being implemented to have a simple structure to stabilize fabrication costs and process yields, and the like.
Description of the Related Art
A band pass filter (BPF) is a filter only allowing a signal having a particular frequency band to pass therethrough and blocking other signals, widely used for the purpose of only selecting a signal having a particular frequency band in a wireless signal transceiver. A frequency band allowed to pass through a band pass filter and a blocked frequency band are classified based on an attenuation frequency, and the characteristics of a band pass filter are determined by an attenuation frequency, an amount of insertion loss, a bandwidth, and the like.
The band pass filter attenuates signals in all frequency bands other than a frequency band used by a wireless transceiver. For a power amplifier, an attenuation frequency band may be a main cause of generating a secondary harmonic component. In general, for band pass filters used to date, designing a usage band has been preferentially considered, and for an attenuation frequency band, an additional circuit for preventing a harmonic component, or the like, may be added.
The use of an additional circuit in order to prevent a harmonic component generated in an attenuation frequency band has an advantage in that the design of a usage frequency band is considered a top priority. However, the additional circuit may disadvantageously increase insertion loss of the band pass filter in a pass frequency band or increase a physical size of the filter.
Cited invention 1 relates to a band pass filter embedded in an integrated passive element substrate in which stop band characteristics are improved in a particular frequency band by generating a parasitic inductance component in a substrate including a via hole structure. Cited invention 2 relates to a method for manufacturing a multilayer filter in which a plurality of dielectric sheets are multilayered and an inductor electrode and a capacitor electrode are connected by a via hole to adjust a passage frequency band, or the like. However, cited inventions 1 and 2 do not disclose a technique of adjusting the amount or shape of via holes or a technique in which a non-conductive region is provided in a portion adjacent to a via hole on a particular surface of a substrate to select an attenuation frequency value.